The present invention relates to an image reading apparatus for reading image information of an original such as a photographic film and an illumination apparatus used in the image reading apparatus.
When dirt such as dust exists on a transparent original or the surface of a photographic film is damaged (scratched), a conventional image reading apparatus for reading image information of the transparent original such as the photographic film reads even the dirt or scratch, so the image degrades owing to the dirt or scratch. In order to solve this problem, an image reading apparatus for correcting image information obtained by a visible light source by using dust/scratch information obtained by image information obtained by an infrared light source has been proposed (Japanese Patent Laid-Open No. 2001-298593). In this image reading apparatus, the visible light source serving as a surface light source such as a fluorescent lamp and the infrared point light source such as an infrared LED chip are arranged on the side surface of a light guide plate.
In the arrangement of the conventional image reading apparatus described above, however, even if light emitted by the visible light source is uniformly guided to an effective light-emitting surface region by a light guide member upon emitting light beams from the respective light sources, light emitted by the infrared light source cannot sufficiently diffuse since the infrared light source is too close to the effective light-emitting region. Hence, the original is nonuniformly irradiated, and the dust/scratch information cannot be accurately obtained.
Recently, along with the development of a communication network and the increases in speed of a computer and capacity of a storage medium, the color image information is required to be processed at a higher resolution. In particular, when color image information is read by a scanner and the like, a demand has arisen for reading the image more accurately at a higher speed and higher resolution.
When reading the image of the photographic film, a demand has arisen for reading the image information of the photographic film having a plurality of frames in a sleeve form more accurately at a higher speed and higher resolution. As a means for reading a film at a higher resolution, an image reading apparatus which has a means for removing the dust or scratch on the film is proposed. The above Japanese Patent Laid-Open No. 2001-298593 is an example of the image reading apparatus. According to this proposal, the light source including the infrared LED for detecting the dust/scratch information and the light source for reading the image information is arranged as a surface light source, so that the image in which the influence of the dust or scratch is reduced can be read.
The form of the image reading apparatus having the function of removing the dust or scratch on the film will be briefly described with reference to FIGS. 15, 16, and 17.
FIG. 15 is a schematic sectional view showing an example of an image input apparatus which can read both a reflecting original such as a document original and the transparent original such as the photographic film. FIG. 16 is a view showing an example of a transparent original light source unit used in the image input apparatus which has the function of removing the dust or scratch as described above.
A transparent original illumination apparatus 500 which is required for reading the transparent original such as the photographic film is arranged in an image reading apparatus 400, and electrically connected to the image reading apparatus 400 via a transparent original light source lighting inverter 507 and I/F cable 515 so as to be controllable from an image reading apparatus control board 503. The transparent original illumination apparatus 500 has a transparent original illumination unit 504 for reading the transparent original.
An optical unit 514 includes a first reflecting mirror 509, second reflecting mirror 510, third reflecting mirror 511, and lens 512 which are required for optically forming the image of the transparent original on a CCD image sensor 513, and a reflecting original illumination light source 508 for irradiating the reflecting original such as the document original, and reads the image while scanning the original in directions indicated by a double-headed arrow shown in FIG. 15 (in a subscanning direction) by the image input apparatus control board 503 and a motor 516.
The CCD image sensor 513 and image input apparatus control board 503 are electrically connected to each other via a signal cable 517. Hence, an electrical signal photoelectrically converted by the CCD image sensor 513 can be obtained as image data by scanning the original while synchronizing the transparent original illumination unit 504 and optical unit 514 by the motor 516.
A transparent plate 519 which exists between the transparent original illumination unit 504 and a film guide 505 on a document glass table 506 uses transparent glass or a diffusion member. As shown in FIG. 16, cold cathode fluorescent lamps (to be referred to as CCFLs hereinafter) 528 and infrared LED arrays 529 for reading the image information on the film original are arranged on the respective end faces in the transparent original illumination unit 504. Note that a reflecting sheet 532 and diffusion sheet 530 are effective to obtain the uniformities of light-emitting surfaces irradiated with respective light sources.
FIG. 17 is an enlarged view of a portion A in FIG. 16, and a schematic view of the light guide member pattern which is used to satisfy the uniformities of surface light sources when the CCFLs 528 and infrared LED arrays 529 are ON. FIG. 18 is a view showing that the incident light emitted by each CCFL 528 is reflected by the reflecting sheet 532, and diffused by a light guide member 531 having triangular grooves to illuminate the original. The taper angle or pitch of each triangular groove in the light guide member 531 is adjusted to obtain a diffusion effect, thereby obtaining the effect of the uniform surface light source. The influence of the dust or scratch can be removed, and a high-quality image can be read by scanning the original while line-sequentially or surface-sequentially switching the CCFLs 528 and infrared LED arrays 529.
In the arrangement of the triangular grooves such as the conventional transparent original light source unit 504 as described above, the uniformity can be obtained by the diffusion effect. However, there is room for improvement about high luminance and high power.
The present invention has been made in consideration of the above problem, and has as its object to provide a high-quality read image from which dust or scratches are removed in an image reading apparatus with a surface light source.
In order to solve the above problem, and achieve the object, according to the first aspect of the present invention, an illumination apparatus comprises a first light source which emits light in a visible range, a second light source which emits light in an invisible range, and a light guide plate which two-dimensionally guides for illumination light beams emitted by the first and second light sources, wherein a distance between an effective light-emitting region of the light guide plate and an arrangement portion of the first light source is different from a distance between the effective light-emitting region and an arrangement portion of the second light source.
According to the second aspect of the present invention, the illumination apparatus comprises a first light source which emits light in a visible range, a second light source which emits light in an invisible range, and a light guide plate which two-dimensionally guides for illumination light beams emitted by the first and second light sources, wherein a first reflecting surface which reflects irradiation light from the second light source into the light guide plate is arranged in the arrangement portion of the second light source.
According to the third aspect of the present invention, the illumination apparatus comprises a first light source which emits light in a visible range, a second light source which emits light in an invisible range, and a light guide plate which two-dimensionally guides for illumination light beams emitted by the first and second light sources, wherein the first and second light sources are juxtaposed along one side of the light guide plate, and a reflecting surface is arranged between the arrangement portions of the first and second light sources.
According to the fourth aspect of the present invention, an image reading apparatus including an original reading light source which illuminates an original, comprises a light guide member which diffuses light from the light source, a light source arranged near a side surface facing a side of a light-emitting surface of the light guide member, and a substantially flat reflecting member arranged on an upper portion of the light guide member to reflect light from the light source into the light guide member, and image reading means for reading an original image illuminated with light from the light source, wherein the light guide member has a plurality of substantially cylindrical grooves to focus the light on the light-emitting surface of the light guide member.
According to the fifth aspect of the present invention, an illumination unit comprises a light guide member which diffuses light, a plurality of cylindrical grooves which are formed in the light guide member, and have generating lines substantially extending in a direction perpendicular to a light-emitting surface, and first and second light sources with different characteristics, which are arranged on a side surface facing the light-emitting surface of the light guide member.
Other objects and advantages besides those discussed above shall be apparent to those skilled in the art from the description of a preferred embodiment of the invention which follows. In the description, reference is made to accompanying drawings, which form a part hereof, and which illustrate an example of the invention. Such example, however, is not exhaustive of the various embodiments of the invention, and therefore reference is made to the claims which follow the description for determining the scope of the invention.